None, this is wildly undefined behavior, even considering GCC's extension and its documentation. I doubt that GCC implementers would be interested in defining t

None, this is wildly undefined behavior, even considering GCC's extension and its documentation. I doubt that GCC implementers would be interested in defining the behavior here. edit: There might be room for some other extension here, but as an other commenter already wrote: 1. functions might not be contiguous in memory 2. the code that you are moving should better be position independent So any such extension should handle these issues one way or an other.